By adding a single character to Twitter's vocabulary nearly four years ago -- # -- Chris Messina unlocked a wealth of useful information in Twitter.

Now he wants to bring the same creation, called a hashtag, to Google+.

Hashtags are terms beginning with the pound sign, also called a hash, for easy identification as a recognizable label. Examples include #wwc hashtag for women's World Cup soccer or the ever-popular #fail hashtag for complaining when things go wrong. By following a particular hashtag, it can be easier to concentrate on content you might be interested in.

Messina sees hashtags as, ideally, a way that people can sift their Google+ "stream"--the collection of posts from all people a Google+ user follows.

"Lots of people have requested the ability to target content [to] their followers based on topic (i.e. only share content to people who are following me AND interested in, say, comics). Since the product doesn't support that kind of targeting, I'm just making something up, like I did with hashtags back in 2007," Messina said in a Google+ post last week. But so far it's a manual process: "So, if you see 3 to 4 topic hashtags at the beginning of my posts (like subject lines but for topics), they're there so people can choose to ignore my post if they're uninterested."

The move is a bit surprising--not that Messina and others would want hashtags, but that Google, a company obsessed with organizing information and making it accessible, didn't do so itself.

Just because Google didn't build the feature into Google+ on day one doesn't mean the company has rejected it, of course. Google is particularly fond of releasing projects as early as possible then updating them as rapidly as possible. Public feedback on Google+ can help steer priorities for the company.

One possibility would be to augment Google+ with tagging abilities that parallel the service's linked names. By typing "+username" into Google+, the service inserts a live link to that user's posts. A "#" operator could similarly link to a live search of Google+ posts using the hashtag, though Google might need to work on presentation to balance how relevant and recent a post is and to show private posts shared with the person doing the searching. People also could follow a particular hashtag the way they can watch a particular circle's comments in the stream.

While Messina brough hashtags to Twitter, tags themselves long predate it. The Flickr photo-sharing service and Delicious bookmarking service use tags extensively, for example.

And Google itself has shown some appreciation for tags. Gmail labels, for example, are tags that can be applied to any message, and Google Docs collections work the same way.

Not everyone is enamored of Messina's idea.

"There's some major cognitive dissonance going on here, seeing Twitter hashtags on Google+," Web developer Adrian Holovaty said in a blog post, complaining that the answer to Twitter's constraints isn't the right answer for Google's social network. "It feels like G+ should have something much more sophisticated and user-friendly," he said.

Messina responded that he's open to new approaches. "I take your point and haven't concluded (personally) that hashtags are right for the medium of G+. But I do think that they serve a purpose, and came out of a transitional medium which still serves a purpose," he said.

Google certainly is paying attention to the hashtag issue. When asked on Q&A site AnyAsq about whether Google+ will support hashtags, Google+ engineer and technical lead Joseph Smarr had this sympathetic response: "Personally, I want this too (and I know Chris Messina agrees, heh), but we don't have anything official to say about this (or pretty much any other specific future features or timelines)."

Google did not immediately return CNET's request for additional comment.

"If you read my original proposal for hashtags (or 'tag channels'), you can see that I was looking to address a lot of the same issues being discussed today on G+," Messina said in a Google+ post. "So, I suppose the question is, can we come up with a better spec for G+ to implement and adopt today?"